Ink jet printers typically include an ink path from an ink supply to a nozzle path. The nozzle path terminates in a nozzle opening from which ink drops are ejected. Ink drop ejection is controlled by pressurizing ink in the ink path with an actuator, which may be, for example, a piezoelectric deflector, a thermal bubble jet generator, or an electro statically deflected element. A typical printhead includes a reservoir and a jetting assembly. The jetting assembly has an array of ink paths with corresponding nozzle openings and associated actuators, and drop ejection from each nozzle opening can be independently controlled. In a drop-on-demand printhead, each actuator is fired to selectively eject a drop at a specific pixel location of an image as the jetting assembly and a printing substrate are moved relative to one another. In high performance jetting assemblies, the nozzle openings typically have a diameter of 50 microns or less, e.g. around 25 microns, are separated at a pitch of 100-300 nozzles/inch, have a resolution of 100 to 3000 dpi or more, and provide drop sizes of about 1 to 70 picoliters (pl) or less. Drop ejection frequency is typically 10 kHz or more.
Hoisington et al. U.S. Pat. No. 5,265,315, the entire contents of which is hereby incorporated by reference, describes a jetting assembly having a semiconductor body and a piezoelectric actuator. The assembly body is made of silicon, which is etched to define ink chambers. Nozzle openings are defined by a separate nozzle plate, which is attached to the silicon body. The piezoelectric actuator has a layer of piezoelectric material, which changes geometry, or bends, in response to an applied voltage. The bending of the piezoelectric layer pressurizes ink in a pumping chamber located along the ink path.
Further examples of jetting assemblies are disclosed in U.S. patent application Ser. No. 10/189,947, entitled “PRINTHEAD,” to Andreas Bibl et al., filed on Jul. 3, 2002, the entire contents of which are hereby incorporated by reference.
The amount of bending that a piezoelectric material exhibits for a given voltage is inversely proportional to the thickness of the material. As a result, as the thickness of the piezoelectric layer increases, the voltage requirement increases. To limit the voltage requirement for a given drop size, the deflecting wall area of the piezoelectric material may be increased. The large piezoelectric wall area may also require a correspondingly large pumping chamber, which can complicate design aspects such as maintenance of small orifice spacing for high-resolution printing.
In general, printheads can include one or more jetting assemblies. Printing systems can print in a single pass of the substrate relative to the printhead, or in multiple passes. Printheads can be used to jet inks and/or other fluids, such as materials used for electronic components (e.g., electrically conductive materials) or color filter materials for flat panel displays, for example.